Download or read book Suppression of Perforated Wall Noise in a Transonic Wind Tunnel and the Effects on Aerodynamic Data written by J. L. Jacocks and published by . This book was released on 1978 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests were conducted to determine the effect of screen overlays installed on the airside test section walls for the purpose of suppressing the wall noise. Data are presented to illustrate that the screens and resulting noise reduction affected the test section logitudinal flow uniformity, plenum-stream calibration, wave cancellation properties of the walls, transition Reynolds number, and shock/boundary-layer interaction. In general, the effect of noise reduction on viscous phenomena was similar to that observed with decreased Reynolds number.
Download or read book A Study of Acoustic Disturbances and Means of Suppression in Ventilated Transonic Wind Tunnel Walls written by N. Sam Dougherty and published by . This book was released on 1977 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of acoustic disturbances and means of suppression from ventilated transonic wall samples was performed in a low-background-noise research tunnel at AEDC. Configurations for ventilation investigated were longitudinally slotted walls, with and without baffles in the slots, slats versus round rods, and perforated walls with normal or inclined circular holes with varied hole sizes and varied diameter/wall thickness ratio. Comparative acoustic data were acquired over a broad range of subsonic Mach numbers. Several of these wall configurations were found to emit intense, discrete whistling noise with overall root-mean-square amplitudes as large as five percent of the free-stream dynamic pressure. In all cases except one, suppressed noise levels not exceeding 0.75 percent of the free-stream dynamic pressure were achieved compared to a background noise level for the tunnel of approximately 0.47 percent with solid test section walls. Noise suppression was accomplished by means of appropriate devices added to the wall samples which could have application to actual transonic wind tunnel test sections. (Author).
Download or read book Perforated Wall Noise in the AEDC PWT 16 ft and 4 ft Transonic Tunnels written by O. P. Credle and published by . This book was released on 1971 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report presents the results of recent studies of noise in Propulsion Wind Tunnel (16T) and Aerodynamic Wind Tunnel (4T). Noise levels in the free stream and at the test section wall were measured in both tunnels as a function of Mach number, Reynolds number, wall angle, and wall porosity. In Tunnel 4T, free-stream noise characteristics were also evaluated with solid (taped) test section walls. Test results revealed that the perforated test section wall holes generate discrete frequency, high energy noise. In Tunnel 16T, there is a critical Mach number range in which a wall hole frequency. Test section noise levels were found to vary slightly with wall angle and significantly with Mach number and wall porosity. The wall porosity corresponding to the minimum noise levels was found in Tunnel 4T. (Author).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book An Experimental Investigation of Techniques to Suppress Edgetones from Perforated Wind Tunnel Walls written by N. Sam Dougherty (Jr.) and published by . This book was released on 1975 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerodynamic Characteristics of Perforated Walls for Transonic Wind Tunnels written by J. L. Jacocks and published by . This book was released on 1977 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: A combined experimental-theoretical approach is developed for determination of the crossflow characteristics of ventilated walls. The technique is based on measurement of static pressures at the boundaries of a two-dimensional flow, calculation of the interior flow properties with Murman- Cole type finite difference techniques, and calculation of the boundary-layer development on and mass flux distribution through the ventilated wall using Patankar-Spalding type solution techniques. Results verify the validity of assuming proportionality between local pressure and flow angle as a boundary condition for wall interference estimates. However, it is also shown that the thickness of the boundary layer represents a dominant influence on the perforated wall characteristics, with both the slope and intercept of the characteristic being dependent on the boundary layer. The effects on the wall characteristics of suppressing the edgetone noise by use of screen overlays or splitter plates within discrete holes are documented.
Download or read book An Experimental Investigation of Techniques to Suppress Edgetones from Perforated Wind Tunnel Walls written by and published by . This book was released on 1975 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aerodynamic noise emitted by perforated walls in transonic wind tunnels has been under study for several years at AEDC. This report presents a summary of recent experimental tests to suppress perforated wall noise in transonic test sections. The mechanism of noise generation from perforated walls having 60-deg inclined holes is the edgetone phenomenon where the shear layer over each hole interacts with the trailing edge to produce intense tones at discrete frequencies. Noise reduction was achieved with several modified wall samples in the 6-in. tunnel at resonance conditions.
Download or read book Noise Generation in Transonic Wind Tunnels written by M. O. Varner and published by . This book was released on 1975 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an attempt to determine the parameters characterizing the noise environment in transonic tunnels, noise-generating mechanisms for porous-wall tunnels with 60-deg inclined holes were isolated and studied. The noise environment in the test section is separated into three distinct parts: the noise due to jet flow through the porous walls, a wall hole-tunnel resonance phenomena, and the turbulent boundary layer on the test section walls and in the diffuser. Each part is analyzed separately for the effects of aerodynamic and geometric flow constraints on the frequency and power characteristics. The contribution of each of the acoustic models to the test section free-stream fluctuating pressure level is also examined.
Download or read book A Study of Acoustic Disturbances and Means of Suppression in Ventilated Transonic Wind Tunnel Walls written by N. S Dougherty (Jr) and published by . This book was released on 1977 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of acoustic disturbances and means of suppression from ventilated transonic wall samples was performed in a low-background-noise research tunnel at AEDC. Configurations for ventilation investigated were longitudinally slotted walls, with and without baffles in the slots, slats versus round rods, and perforated walls with normal or inclined circular holes with varied hole sizes and varied diameter/wall thickness ratio. Comparative acoustic data were acquired over a broad range of subsonic Mach numbers. Several of these wall configurations were found to emit intense, discrete whistling noise with overall root-mean-square amplitudes as large as five percent of the free-stream dynamic pressure. In all cases except one, suppressed noise levels not exceeding 0.75 percent of the free-stream dynamic pressure were achieved compared to a background noise level for the tunnel of approximately 0.47 percent with solid test section walls. Noise suppression was accomplished by means of appropriate devices added to the wall samples which could have application to actual transonic wind tunnel test sections. (Author).
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1984 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1975 with total page 882 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1971 with total page 1388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications Cumulative Index written by United States. Superintendent of Documents and published by . This book was released on 1976 with total page 1466 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Perforated Wall Noise in the AEDC PWT 16 ft and 4 ft Transonic Tunnels written by and published by . This book was released on 1971 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report presents the results of recent studies of noise in Propulsion Wind Tunnel (16T) and Aerodynamic Wind Tunnel (4T). Noise levels in the free stream and at the test section wall were measured in both tunnels as a function of Mach number, Reynolds number, wall angle, and wall porosity. In Tunnel 4T, free-stream noise characteristics were also evaluated with solid (taped) test section walls. Test results revealed that the perforated test section wall holes generate discrete frequency, high energy noise. In Tunnel 16T, there is a critical Mach number range in which a wall hole frequency. Test section noise levels were found to vary slightly with wall angle and significantly with Mach number and wall porosity. The wall porosity corresponding to the minimum noise levels was found in Tunnel 4T. (Author).
Download or read book Government reports annual index written by and published by . This book was released on 199? with total page 1190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Forward Velocity Effects on Fan Noise and the Suppression Characteristics of Advanced Inlets as Measured in the NASA Ames 40 by 80 Foot Wind Tunnel Acoustic Data Report written by and published by . This book was released on 1981 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
